I have a Main Activity with a bunch of Fragments connected to it.
One of the fragments has to be able to recieve data from MainActivity after it has been loaded in the FragmentTransaction and committed.
What is the best way to call a method in that specific fragment?
Do I have to implement a Interface and include it in the MainActivty just for this one fragment? Is there a better way? Can someone point me in the correct direction?
What I have tried now : (Failing at settings ContactsInterface in the MainActivity)
ContactsInterface
public interface ContactsInterface {
void notifyDenied();
void notifyGranted();
}
Fragment
Class.... implements ContactsInterface...
#Override
public void notifyDenied() {
Log.d("DENIED", "DENIED CALLBACK");
}
#Override
public void notifyGranted() {
Log.d("GRANTED", "GRANTED CALLBACK");
}
Main Activity
try {
contactsInterface = (ContactsInterface) this.getApplicationContext();
} catch (ClassCastException e) {
throw new ClassCastException(this.toString()
+ " Needs to implement the methods");
}
Last example throws an ClassCastException.
You need to cast the fragment itself not the Application Context.
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
ExampleFragment fragment = new ExampleFragment();
fragmentTransaction.add(R.id.fragment_container, fragment);
fragmentTransaction.commit();
ContactsInterface contactsInterface = (ContactsInterface) fragment;
//contactsInterface.notifyGranted();
//contactsInterface.notifyDenied();
You can get all the active fragments in the FragmentManager and filter for the ones that have the required interface:
supportFragmentManager.fragments
.map { it as? ContactsInterface }
.filterNotNull()
.forEach {
it.notifyDenied()
}
or if you need to use Java:
List<Fragment> fragments = getSupportFragmentManager().getFragments();
for(fragment : fragments) {
if(fragment instanceof ContactsInterface) {
((ContactsInterface)fragment).notifyDenied();
}
}
You may want to also fail (hard or soft) if no fragments are found.
The advantage of doing this is that you don't care how the fragment was started (manually or by layout) and also don't have to care about reconnecting when the activity restarts for example.
This library may be useful to you.
You should do something like this in your fragment:
#Override
public void onCreateView() {
super.onStart();
EventBus.getDefault().register(this);
}
#Override
public void onDestroyView() {
super.onStop();
EventBus.getDefault().unregister(this);
}
#Subscribe(threadMode = ThreadMode.MAIN)
public void onMessageEvent(MessageEvent event) {/* Do something */};
MessageEvent is just an example, you can use whatever structure you want.
in the Activity you post messages like this:
EventBus.getDefault().post(new MessageEvent());
Check the documentation of the library to have a better idea and use a better approach to your case.
you can use onCreate() and onDestroy() instead. That depends on your logic and you you are updating the view of the fragment when you receive new messages from the Activity.
Happy coding :).
Related
I have two different layouts, for two different fragments, but in single activity. I am using onAttachFragment callback, but I am unable to use both the interfaces simultaneously.
public interface AvInterface{
public void onMessageRead(String data);
}
public interface WeInterface{
public void onMessageRead(String data);
}
somefunction(){
avInterface.onMessageRead("14221322345124");
weInterface.onMessageRead("142620405958");
}
public void onAttachFragment(Fragment fragment) {
super.onAttachFragment(fragment);
try {
avaInterface = (AvInterface) fragment;
weInterface = (WeInterface) fragment;
}
catch (ClassCastException e) {
//throw new ClassCastException(fragment.toString()+" must override AvInterface");
}
}
You should use the onAttach() callback in Fragment.
From onAttachFragment() doc :
Called when a fragment is attached as a child of this fragment.
This is a callback provided when you attach a child fragment is attached to the current fragment.
I think you are hosting both fragments in the activity and hence use onAttach() to get access to the interface to communicate with the activity.
Like mentioned by #Arka Prava Basu, you only need one Interafce and you do something like the following in your parent activity
if(fragment InstanceOf fragmentA){
dosomething();
}else{
dosomethingelse()
}
I hope you get the idea.
I read Android documentation on how to add a Fragment to an activty. It says that to add a Fragment to an Activty I should write this code inside the Activity class:
FragmentManager fragmentManager = getFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager.beginTransaction();
ExampleFragment fragment = new ExampleFragment();
fragmentTransaction.add(R.id.fragment_container, fragment);
fragmentTransaction.commit();
but this is for android.app.Fragment class.
For android.support.v4.Fragment, documentation say that instead of getFragmentManager() I should call getSupportFragmentManager() and that Activity must extends FragmentActivty.
So I did this change, and now this is my activity code:
public class ExampleActivity extends AppCompactActivity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_fragment);
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction =
fragmentManager.beginTransaction();
ExampleFragment fragment = new ExampleFragment();
fragmentTransaction.add(R.id.fragment_container, fragment);
fragmentTransaction.commit();
}
}
AppCompactActivity is a subclass of FragmentActivity so I respected the constraints.
The problem is that if I run my application I get this error:
java.lang.RuntimeException:
com.myapplication.ExampleActivity#13388c6 must implement OnFragmentInteractionListener
I typed OnFragmentInteractionListener on Android doc web search and this is what I get:
Immediately below there is the link
https://developer.android.com/training/basics/fragments/communicating.html
that shows me a guide to communication between fragments. It speaks about ListFragment and I don't care it.
I'm very very confuse because every time I read documentation there are always things that force me to make internet search to find workaround or fix to problems.
Is there a persone that can explain me first how to fix this problem.
From the tutorial, you can read the following:
In order to receive event callbacks from the fragment, the activity
that hosts it must implement the interface defined in the fragment
class.
So, implement it in your Activity with something like this in your fragment:
public static class MainActivity extends Activity
implements HeadlinesFragment.OnHeadlineSelectedListener{
...
public void onArticleSelected(int position) {
// The user selected the headline of an article from the HeadlinesFragment
// Do something here to display that article
}
}
Why did you need it? Because you've forced the host activity to implement it with something like this:
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
// This makes sure that the container activity has implemented
// the callback interface. If not, it throws an exception
try {
mCallback = (OnHeadlineSelectedListener) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ " must implement OnHeadlineSelectedListener");
}
}
Here is my main activity. I followed this guide about Fragments correctly. When I click "Back" button, my application is closed instead of returning to the MainScreenFragment. Why is this happening and why addToBackStack() doesn't work?
public class MainScreenActivity extends ActionBarActivity implements MainScreenFragment.OnFrameChoiced {
private MainScreenFragment mainScreenFragment;
private AddWordsFragment addWordsFragment;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main_screen);
mainScreenFragment = new MainScreenFragment();
addWordsFragment = new AddWordsFragment();
FragmentManager fm = getFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
ft.add(R.id.container, mainScreenFragment).addToBackStack(null).commit();
}
#Override
public void choiceFrame(int id) {
switch (id) {
case R.id.add_new_words_frame:
FragmentManager fm = getFragmentManager();
FragmentTransaction ft = fm.beginTransaction();
ft.replace(R.id.container, addWordsFragment).addToBackStack(null).commit();
fm.executePendingTransactions();
break;
}
}
P.S. I tried to use a solution from this topic, but It still doesn't work.
did you try overriding the back like below:
#overide
public void onBackPressed(){
FragmentManager fm = getSupportFragmentManager();
if (fm.getBackStackEntryCount() > 1) {
fm.popBackStack();
} else {
finish();
}
}
(I know you have picked up your desirable answer, but I have found a little more against this problem)
Though as Android official site has documented:
By calling addToBackStack(), the replace transaction is saved to the back stack so the user can reverse the transaction and bring back the previous fragment by pressing the Backbutton.
But as a matter of fact, this is in a precondition that you are using the standard android activity, specifically, the android.app.Activity. Because this methods in android.app.Activity will work when Backbutton is pressed:
public void onBackPressed() {
if (mActionBar != null && mActionBar.collapseActionView()) {
return;
}
if (!mFragments.getFragmentManager().popBackStackImmediate()) {
finishAfterTransition();
}
}
But, if you are extending your xxxxActivity from someone else, for example, the AppCompatActivity, FragmentActivity, ActionBarActivity, it will be another story, because in FragmentActivity, onBackPressed() method is totally overrode:
public void onBackPressed() {
if (!mFragments.getSupportFragmentManager().popBackStackImmediate()) {
supportFinishAfterTransition();
}
}
Note that mFragments.getFragmentManager() is replaced by mFragments.getSupportFragmentManager(), so in cases like this, you should begin your FragmentTransaction using getSupportFragmentManager() of the Activity. and as a consequence of that, you don't have to override onBackPressed method in your Activity.
BTW, ActionBarActivity extends AppCompatActivity extends FragmentActivity,they all come from the support library, you know what I mean, remember to use getSupportFragmentManager() instead of getFragmentManager() when using support library in order to get the compatible behavior.
I've a activity which basically is :
public class FragmentContainer extends FragmentActivityBase implements IRefreshListener {
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (getIntent().getExtras() == null
|| getIntent().getExtras().get("type") == null) {
showProductList();
}
else
{
if (getIntent().getExtras().get("type").equals("customer"))
showCustomerList();
}
#Override
public void showProductList() {
FragmentManager fragmentManager = getSupportFragmentManager();
FragmentTransaction fragmentTransaction = fragmentManager
.beginTransaction();
// load the product list
ProductList fragment = new ProductList();
fragmentTransaction.replace(R.id.fragment_container, fragment)
.addToBackStack(null);
fragmentTransaction.commit();
}
.....
}
in the fragment, I use onCreateView to get intent and then I create my view.
If I need to change the fragment, I get the reference to the parent Activity (taken from onAttach) and I call method referenced by the IRefreshListener.
like :
IRefreshListener mCallback;
#Override
public void onAttach(Activity activity) {
super.onAttach(activity);
// This makes sure that the container activity has implemented
// the callback interface. If not, it throws an exception.
try {
mCallback = (IRefreshListener) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString()
+ " must implement IRefreshListener");
}
}
public void callCustomer() {
mCallback.showCustomerList();
}
It works but whne I change the orientation, even I use setRetainInstance(true) it will be reseted.
I have 2 questions :
Do I use the good pattern to manage my application. The big activity which contains one fragment become bigger with the time
How should I handle orientation change ?
Regards
I do not find this pattern is more perfect or best one, although it is or was a suggestion from Google. Because it could be a worse coding style if fragment knows particular activity or listeners, you might write more and more code, when you wanna to let your fragment know more its "container" or "parents". Will the fragment later be used for other activity which has not been implemented with IRefreshListener etc, you will code much more.
My introduce is using Otto-Bus or Event-Bus. You can just send message from one to one. Every one doesn't have to know each other.
I have an activity with dynamic fragments in it. I need to run some code after a fragment is removed but remove(myFragment).commit() is executed asynchronously and i cant know when exactly the fragment is removed.Here is my code:
final FragmentTransaction ft = getFragmentManager().beginTransaction();
ft.remove(myFragment).commit();
//wait until the fragment is removed and then execute rest of my code
From the documentation:
public abstract int commit ()
Schedules a commit of this transaction. The commit does not happen
immediately; it will be scheduled as work on the main thread to be
done the next time that thread is ready.
What if you use the fragment's onDetach method to call the activity and tell it its done?
class MyFrag extends Fragment {
private Activity act;
#Override
public void onAttach(Activity activity) {
act = activity;
}
#Override
public void onDetatch() {
act.fragGone();
}
}
And in the activity:
public void fragGone() {
//do something, update a boolean, refresh view, etc.
}
You could try using the onDetached() callback of the fragment. This will be called whenever it is removed from its Activity.
Use onAttach() to check when the fragment is attached to the Activity and use onDettach() to check when the fragment is dettached to the activity.
Using the onDettach() you can also check to update or not views, data, etc in this way:
#Override
public void onDetach() {
super.onDetach();
synchronized (mLock) {
mReady = false;
}
}